Method of producing gasoline having improved distribution of anti-knock capability



Jan. 8, 1963 Filed March 20, 1959 FIG.|

4 Sheets-Sheet 1 Blend Octane Number 3-, 90.8 Octane Number A Reformate Tram E Q l80-380E Naphtha 2 8 (Heavy Naphrha) U C 2 E O 99.8 Octane Number 8 a Reformate from 8 IOOZ-BBOENaphtha O a v U 3 a:

50 I00 I50 200 250 300 350 400 E Mean Average Boiling Point I I l MABP= Mean Average Boiling Point u= 2 I05 5 A a. u: 2 E 2; Blend Octane Number Q .C 2 E d m', 2m 0 lm o O a (LIL. m a .C o m LL' CLLL' 2 0 2 r0 3 m u.- 9 "2{ "2m EN 8: 2 0. u.- l m 0's 6.. a 4% l 2 *3 4 -E *5ls *7 si- 9 I0 so so so so so I00 Volume BL-90.8 Reformate from l-380F. Naphfha l/Vl/E/VZ'OH. Vernon O.Bowles AGENT- Jan. 8, 19 63 V. O. BOWLES UCING GASOLINE METHOD OF PROD HAVING IMPROVED DISTRIBUTION OF ANTI-KNOCK CAPABILITY Filed March 20, 1959 4 Sheets-Sheet 2 MABP=Meon Average Boiling Point r e mm m m I A mmmm 8 M32 L FMS m 19E n A ra 6 2 mm A m EMS 5 m m 2 F u m n 52% m n 5%; m n .rwQ u m .32 A." e F m 3 59 a Ems). momw m 05 52 w u n a a 2 8 9 BnEaz 2530 c2331 IO 20 4o Volume%96.2 Reformafe from |80-380F. Nophfhu IIE MABP= Mean Average Boiling Point .mnEa 2.200 5833.

0 w mrmwm m 552 w B Z5 9 19;. m "w w a $.08. a has): m w m 9&3 H mm; m Ar 0 B s Ema 6 mm; "a" m Em: w 8mm mm; w d n wm h m w 5% T w mu u B mm im. 3 .132 o ldN 2 m. n who a B PLQNM." m Em W M a n a a 2 3 5 Volume 99.8 Reformute from lOO-380F. Nuphthu IIVVENTOR. Vernon QBowles FIG.4

AGENT.

Jan. 8, 1963 v. o. BOWLES 3, 7 6

' METHOD OF PRODUCING GASOLINE HAVING IMPROVED DISTRIBUTION OF ANTI-KNOCK CAPABILITY Filed larch 20, 1959 4 Sheets-Sheet 4 FIG.6

80.3% Reformaie 99.8 Octane Number |9.7% Heavy Straight Run Naphtha Boiling Range l80-380F.

Research Octane Number (I.9cc TEL/gal) q Mean Average Boiling Pom? INVENTOR. Vernon QBowles by w AGENT.

United States Patent ()fiice Patented Jan. 8, 1963 3,072.562 METHOD OF PRODUCING GASOLINE HAVING IMPROVED DISTRIBUTION OF ANTI-KNOCK CAPABILITY Vernon 0. Eowles, Katonah, N.Y., assignor to Socony MobilOil Company, Inc., a corporation of New York Filed Mar. 20, 1959, Ser. No. 800,715 4 Claims. (Cl. 208-93) The present invention relates to the problem which arises when one or more cylinders of certain spark-ignited internal combustion enginesknock although the octane rating of the gasoline supplied to the engine is high enoughmanifold whereby a major portion of the lower boiling fraction of the gasoline goes to the cylinder or cylinders furtherest from the gasoline inlet to the manifold and a major portion of the heaviest fraction of the gasoline goes to the cylinder or cylinders nearest the gasoline inlet to the manifold.

It is manifest that, as a result of manifold distillation, when the octane ratings of the various fractions differ. those fractions the octane ratingsof which are below that required for knock-free operation of the engine will cause those cylinders into which these fractions flow to knock. This is more readily recognized by reference to FIGURE 1.

Curve A of FIGURE 1 represents the relation of the octane rating of fractions of a gasoline having an octane rating of 90.8 (Research-H9 cc. TEL/gal.) and the indicated mean average boiling point (M.A.B.P.). It'will be seen, by reference to curve A, that those fractions of the 90.8 O.N. gasoline having a M.A.B.P. between about 150 F. and about 260 F. have octane rating of the order of 70.8 to 87.3 and represent about 52 percent of the gasoline (see FIGURE 2 and Table I). In the ensuing discussion this will be referred to as the low octane valley, Where the width of the valley is the percent by volume of the full boiling range gasoline in the valley and the depth of the valley is the weighted octane number of the total valley fraction. It is-to be noted that thereis one heavier, i.e., higher boiling, fraction the octanenumber of which is slightly under 90.8 but the octane number of this fraction is very near the octane number of the blend, and, not being in the valley,'contributes little towards malperformance. This difiiculty can partly be overcome by reforming the straight run gasoline to a higher octane level. Thus, for example, when the straight run gasoline is reformed to 96.2 octane, number (Research+1.9 cc. TEL/ gal.) only 42.5 percent of the gasoline has an octane rating below 90.8 (see FIG- URE 3 and Table II). Furthermore, when straight run gasoline is reformed to 99.8 octane number (Research-H9 cc. TEL/gal), then only about 20 percentof the total gasoline has an octane rating below about190.8 (see FIGURE'4 and Table III).

Table l 90.8 ON, reformate from In excess 0190.8 O.N.

180380 naphtha Part; of Wtd. Fraction Wtd. total O.N. O.N. of total- O.N. O.N. reformate reformate 105 103. 3 10. 8 105 103. 3 10. 8 .110 87.3 9. 6 105 94. 3 9. 9 .100 79. 5 8.0 .100 90.3 9.0 .105 84. 5 8. 9 095 101. 3 9. 6 .100 70. 8 7.1 075 120. 0 9.0 105 84. 3 8. 9 105 94. 3 9. 9 480 (100. 7) 48. 3 90. 3 9:0 .035 101. 3 0. 6 .075 120. 0 9. 0 Below 908 O.N.

1 Weighted octane number. p V. V 2 It will be observed that this fraction although hav1ng an octane rating less than 00 8 has been included with the fractions havmg'octane ratings in excess of 90 8. This has been done because the fraction 1n question is a high boiling fraction and its effect Wl1l b6 compensated by the other high boiling fractions having an octane rating in excess of 90.8

Table 11 96.2 O.N. reformate from 180- In excess of 90.8 O.N. 380 F. naphtha Part of Wtd. Fraction Wtd. total O.N. O.N. of total O.N. O.N. reformate reformate .110 100.0 11.00 575 (106. 7) 61. 34 100 103. 3' 10.33 .18 120.2 21. 64 Q Below 90.8 O.N i 1. 000 90. 20. i Y 7 1 Wtd. O.N.-Weighted octane number.

Table III 1 96.2 ON. reformate from 100 In excess of 90.8 O.N.

380 F. naphtha Partot Wtd. Fraction Wtd. total O.N. O.N. of total O.N. O.N.! reformate I refer-mate 100 101. s 10. 4s 100 101. s 10. 43 .100 92. 5 9. 25 .100 .92. 5 9. 25 100 77.8 7.78 100 92. 3 9. 23 .100 a 81.5 1 8.15 .100 9118 9. 98 .100 02.3 0,23, .095 107.3 10.19 g .100 99.8 9.98 .100 114.0 11.11 .005 v 107.3 10.73 .005 112.7 1071a .100 111. 0 11. 40 .110 109.7 12, 07

Less than 90.8 O.N.

. 100 77. s 7 7s .100 r 81.5 8.15 .200 i 79.7) 15.93

1 Wtcl. O.N.-Weighted octane'number.

While reforming to a total octane number higher than the required octane number reduces the volume of the fraction of the total gasoline having an octane rating lower than the require octane rating, such a method for overcoming the problem of manifold distillation is costly and wasteful as will become evident from the following discussion.

One hundred barrels of gasoline having an octane rating of 90.8 (Research-+1.9 cc. TEL/ gal.) represents to the problem of manifold distillation is provided by reforming a fraction of the whole straight run naphtha, preferably the fraction having an initial boiling point within the range of about 160 and about 220 F. and an end boiling point within the range of about 330 and about 420 F. under reforming conditions of severity such as to reduce the width of the octane valley to a practical minimum. In other words, the hereinbefore defined fraction of a straight run naphtha is reformed 9,080 octane barrels. When the straight run gasoline is under reforming conditions to produce a reforate having reformed to 96.2 octane number (Research+l.9 cc. an octane rating (Research-{-19 cc. TEL/gal.) greater TEL/gaL) one hundred barrels feplesents 0 Octane than the required octane rating in which the width and barrels. Similarly, when the straight run gasoline is depth of the octane valley are markedly reduced when formed to 99.8 octane number (Research-{4.9 cc. TEL/ compared to the octane valley in a reformate of required gal.) one hundred barrels represents 9,980 octane barrels. octane rating. The reformate having a markedly re- Thus, although the etfect'of manifold distillation tends duced or, when economically practical, no octane valley to be overcome by reforming to an octane high en ugh is then blended with an amount of unreformed heavy to minimize the octane valley in the octane number vs. fraction of the straight run naphtha to produce a blend boiling point curve an appreciable number of octane having the required octane rating. (Heavy naphtha is barrels are given away. The width and depth of the that fraction having an initial boiling point within the low octane number valley as well as the number f range of about 160 to about 325 F., preferably not octane barrels given away at various octane levels is below 225 F. and an end boiling point within the range manifest by inspection of Table IV. In-passing it should of about 300 to about 425 F.) Preferably, the rebe observed that the octane valley occurs in the lower formate is blended with a heavy naphtha fraction having boiling fraction of the blend and results in low front a high initial boiling point, i.e., having an initial boiling end octane number in spite of the high octane number point within the range of about 225 to about 275 F. of the lightest (C fraction. It is also worthy of m nor higher and an end boiling point within the range of tion that TEL (tetraethyl lead) distillation tends to about 330 to about 420 F. For example, to make starve the front end fraction of TEL accentuating the gasoline having an octane rating of 90.2 (Research+l.9 octane rating deficiency of the front end and inefficiently cc. TEL/ gal.) the reformate from a straight run naphtha provides an excessive amount of TEL to the tail-end from which a part of the heavy naphtha has been refractions. moved and having a boiling range of 100 to 380 F. is Table IV mixed with a separated fraction of straight run naphtha [Required (Research+1 9 w TELIgaLFQM] boiling in the range of 180 to 380 F., i.e., heavy naphtha, in the proportion set forth in Table V. Resegarch iiigiiiig %IZGSSO%CIIE%II1B, Table V Tat/2:1. fidtat" tater: diam: age /enemas:ga gsta: harsher:attests.

( p rLLn), B.R 1s0-3s0 F. equals 19.7 percent] g (vol.) lightest boiling fraction 50% (vol.) heaviest boiling fraction 99.8 .20 79.7 900 Fraction Frac- O.N. oi Wtd. Fraction Frac- O.N. of W td.

No. tion of traction O.N.. of 0 tion of traction O.N. of Thus, while manifold distillation can be overcome by 45 blend nacho blend reforming to a higher octane number it is ineificient bea cause some of the cylinders are supplied with fuel the ;3; 33;; it; :8? 33:8 octane rating of which is in considerable excess of the .03 91.5 2.75 .025 97.5 7- octane rating which these cylinders can advantageously :28 35:8 $138 18;? 3Z3 use and excess octane barrels essentially are given away. 3.18 Thus, it is manifest that an eificient method of compen- 188 Q8 fig 18%;; 3; sating or overcoming the'efiects of manifold distilla- 018 tion is necessary if valuable octane barrels are not to be 43434 45,77 given away.

One typical conventional method of processing involves the blending of normal 0.; hydrocarbons, light straight run gasoline, a reformate having an octane num ber (Research-{4.9 cc. TEL/gal.) of 94.1, and a second reformate having an octane number (Research+1.9 cc. TEL/ gal.) of 96.2 in the following proportions to provide a blend having an octane rating of 90.5 (Research-{4.9 oc. TEL/gal).

Percent Normal C 4 Light straight run naphtha (78.7 O.N.) 30 94.1 O.N. reformat Y 40 96.2 O.N. reform 26 NOTE.Calculatcd octane of light 50%=87.9. heavy 50%=9l.5. It will be observed that there are no excess octane barrels in the blend as prepared in the manner described. Consideration of the curve of FIGURE 5 will also make it evident that even when manifold distillation occurs there will be a more uniform distribution of the high, i.e., above 90.2, and the low, i.e., below 90.2, fractions of the blend to all of the cylinders of the engine. This is because the octane number of the lower boiling fifty percent of the blend is more nearly equal to the octane rating of the higher fifty percent fraction. It will be observed that the width of the octane valley has been reduced to about 25 volume percent of the blend composed, as shown in FIGURE 6, of the fractions having a M.A.B.P. (mean average boiling point) of about to about 210 F. while a balancing fraction of about 10 volume percent having a M.A.B.P. of about 310 to about 350 F., and also having an octane number less than that of the blend (90.2) has resulted from introducing the unreformed heavy naphtha into the blend. Those skilled in the art Calculated octane of 5 will also observe that the octane rating of the lighter fifty percent fraction of the blend is 87.9 which is only 3.6 octane numbers lower than the octane rating (91.5) of the heavier, fifty percent fraction of the blend. The difference between the actual octane number of the blend (90.2) and the calculated value (89.7) is the effect of blending appreciation in the light of present knowledge. This blending appreciation appears to apply equally to the light and to the heavy fifty percent fractions of the blend. Although all of the fuel passing through the engine manifold does not distill (a portion flows to the cylinders as a mist or fog) it is to be noted that any tetraethyl lead( which is relatively high boiling) in the blend will tend to remain with the higher boiling fifty percent fraction and appreciate the octane value of this fraction while concurrently depreciating the octane value of the lighter (manifold distilled) fifty percent fraction. The combination of tetraethyl lead distillation and fuel mist tends to be compensating. Thus, the comparison of the octane number of the lighter fifty percent fraction and the octane number of the heavier fifty percent fraction is a useful indication of the engine performance to be expected and achieved. Alternately, a satisfactory blend of characteristics similar to that of the aforedescribed blend can be made by fractionating a straight run naphtha to obtain a C ,280 F. cut and a 280 to 380 P. fraction. All of the C 280 F. cut and about 62.5 percent of the 280-380 F. fraction is reformed to provide a reformate having an octane rating (Research-[4.9 cc. T EL/gal.) of about 99.8. This reformate is then blended with the unreformed remainder of the 280-380 F. fraction. Thus, for example, the straight run naphtha can be fractionated to give the following cuts in the ratio indicated.

Fraction Percent 0.N. (R.+

volume 1.9 cc.)

C5280F 61. 3 Immaterial 280-{380FQ. 38. 7 51 Since the yield when reforming the C 380 P. fraction is known, it can readily be calculated how much of the 280-380 F. fraction is to be reformed with the C to 280 F. to 99.8 ON. (R+1.9 cc.).

Reformate required 99.8 ON (R+1.9 cc.) to make 100 bbls. of 90.2 ON. (R+1.9 cc.) when blended with 19.7 bbls. of 280380 F. fraction having O.N. (R+1.9 cc.) of 5l 80.3 bbls.

Yield of 99.8 ON. reformate from C -280 F. enriched C 380 F. straight run naphtha fraction-69.4% vol.

=1151 bbls. of 05-380 F./100 bbls. of 99.8,0.N.

0-694 reformate Bbls. of C 280 F./ 100 bbls. C -380 F. straight run naphtha=6l.3

Bbls. of C 380 F./ 100 bbls. C -380 F. straight run naphtha to be processed=24.2

Accordingly, the present invention provides for reforming substantially all of the C to 280 F. fraction of a straight run naphtha and a portion of the 280 to 380 F. fraction of a straight run naphtha to the extinction or minimizing of the octane valley in the curve representing the relation between octane rating and mean average boiling point of various fractions of the reformed gasoline and blending with the reformate-so obtained, the unreformed remainder of the 280 to 380 F. fraction of straight run naphtha to produce a blend having the required octane rating and an improved distribution of the octane rating over the distribution range of the blend.

Stated in another way the present invention-provides for reforming substantially all of the C to 280 P. fraction ofa straight run naphtha and a portion of the 280 to 380 P. fraction of a straight run naphtha to an octane rating higher than the required octane rating of a gasoline to eliminate or minimize the portion of the C to 280 F. having an octane rating substantially less, i.e., more than two octane units less, than the required octane rating of a gasoline and blending with the reformate so produced aportion of the 280 to 380 F. boiling range fraction of a straight run naphtha to produce a gasoline blend having the requiredoctane rating, the aforesaid blend having not more than about 30 volume percent of the total blend boiling in the range C to 280 F., having an octane rating substantially less than the required octane rating of the blend, the aforesaid blend having not more than about 20 percent of the total blend boiling in the range 280 F. to the end boiling point of the blend having an octane rating substantially less than the required octane rating of the blend. The amount of the 280-380 F. fraction of the straight run naphtha which can be blended with the reformate from the reforming of the C to 280 F. and a portion of the 280 -3 F. fraction of straight run naphtha is readily determined from the equation N :octane rating of 280 to 380 F. fraction of straight run naphtha R=octane rating of reformate from C to 380 F. fraction of straight run naphtha K=,octane rating of blend X =percent of 280 to 380 P. fraction in blend -X=percent of reformate from C to 380 F. fraction The C 380 F. fraction to be reformed consists of all of the C to 280 F. fraction and the balance of the 280 to 380 P. not used in the blend as unreformed, straight run naphtha. In other Words, the volume and'the severity of reforming conditions is dependent upon the required octane rating of the blend and the octane rating of the 280 to 380 F. fraction of the unreformed, straight run naphtha. i

A modification of the foregoing comprises fractionating the straight run naphtha into a C to F. fraction (A); a 160 to 320 F. fraction (B); and a 320380 F. fraction (C).

All of the 160 to 320 F. fraction (B) plus a portion ofthe 320 to 380 F. fraction (C) is reformed. to an octane rating greater than the required octane rating of the finished gasoline dependent upon the octane ratings of fractions A and C.

Accordingly, the present invention provides for (l) fractionating a straight run gasoline into at least two fractions the first fraction having an end boiling point of about 280 F. and the second fraction having an end boiling point of not more than about 380 F.; (2) reforming all of the said first fraction and a portion of the second fraction to obtain a reformate having an octane rating (Research-{-19 cc. TEL) higher than the required octane of the finished gasoline; (3) mixing said reformate and the balance of said second fraction to provide a blend having substantially the required octane rating, the balance of said second fraction to be admixed with the reformate being determined by the equation R octane rating of the reformate obtained from the first and a portion of the second fraction K =the required octane rating of the blend, and

X=the percent of unreformed second fraction in the blend Accordingly, the present invention provides a method for producing motor gasoline not more than about 30 percent of which has an octane rating more than 3 units below the octane rating of the whole gasoline which comprises fractionating a straight run gasoline into at least a light naphtha and a heavy naphtha having an initial boiling point in the range of the 160 to 325 F. and preferably not lower than 225 F., reforming at least a portion of the light naphtha together with a portion of the high boiling fraction top roduce a reformate having an octane rating higher than the required octane rating (R+1.9 cc. TEL) of the blend and mixing the unreformed straight run gasoline with the aforesaid reformate to provide a blend having the required octane rating.

I claim:

1. A method of producing blended gasoline comprising catalytic reformate, straight run gasoline, and tetraethyl lead and having a required octane rating which comprises fractionating straight run naphtha to obtain fraction A comprising C and heavier hydrocarbons having an end boiling point of about 160 F., fraction B comprising hydrocarbons boiling in the range of about 160 to about 320 F., and fraction C comprising hydrocarbons boiling in the range of about 320 to about 380 F., reforming all fraction B and a portion of fraction C, separating a reformate comprising C and heavier hydrocarbons having an octane rating higher than said required octane rating of the aforesaid blended gasoline, mixing said reformate, fraction A, and the unreformed portion of fraction C, and obtaining blended gasoline having the aforesaid required octane rating of which blended gasoline not more than 30 percent by volume has an octane rating more than three octane rating units below the octane rating of the blended gasoline.

2. A method of producing blended gasoline comprising catalytic reformate and straight run gasoline and having a required octane rating which comprises fractionating a straight run gasoline to obtain a light fraction comprising C and heavier hydrocarbons having an end boiling point of about 280 F., and a heavy fraction having a boiling range of about 280 to about 380 F., catalytically reforming substantially all of said light fraction and a minor portion of said heavy fraction to obtain C to 280 F. reformate having a minimum portion thereof more than two octane units less than the required octane rating of a blend of C and heavier reformate and the major portion of said heavy fraction, blending said reformate and the major portion of said heavy fraction, and obtaining a gasoline blend having the aforesaid required octane rating, having not more than 30 percent by volume boiling in the range C to 280 F., and said not more than 30 percent having a rating more than three octane units below the required octane rating of said gasoline blend.

3. A method of producing blended gasoline comprising catalytic reformate and straight run gasoline and having a required octane rating which comprises fractionating straight run gasoline to obtain a heavy fraction having a boiling range of about 280 F. to about 380 F., and a light fraction having an end boiling point of about 280 F., catalytically reforming substantially all of the hydro- .carbons of said light fraction boiling in the range of C to 280 F. and only a portion of the aforesaid heavy fraction under reforming conditions of temperature and liquid hourly space velocity to minimize the octane valley in the curve representing the relation between octane rating and means average boiling point of the fractions of said reformedC to 280 F. hydrocarbons to obtain a C reformate having a minimized octane valley, blending said reformed hydrocarbons with the balance of the unreforrned heavy fraction of the aforesaid straight run gasoline and obtaining a gasoline blend of which gasoline blend not more than about thirty percent thereof boiling in the boiling range of the lightest fifty percent has an octane rating 5 to 25 octane rating units below the aforesaid required octane rating.

4. A method of producing blended gasoline comprising catalytic reformate and straight run gasoline and having a required octane rating which comprises fractionating straight run gasoline to obtain a light fraction comprising C and heavier hydrocarbons and having an end boiling point in the range of 225 to about 325 F. and a heavy fraction having an initial boiling point about the same as the end boiling point of the contemporaneously fractionated light fraction and an end boiling point in the range of about 300 to about 420 F., catalytically reforming substantially all of said light fraction and a minor portion of said heavy fraction, obtaining a reformate comprising C and heavier hydrocarbons having a minor portion thereof more than two octane units less than the required octane rating of a blend of C and heavier reformate and the major portion of said heavy fraction, mixing said reformate and the major portion of said heavy fraction, and obtaining a gasoline blend comprising C and heavier hydrocarbons having not more than 30 percent by volume of the hydrocarbons boiling in the range of C to 280 F. having an octane rating substantially less than the octane rating of said gasoline blend and having not more than about 20 percent by volume of said gasoline blend boiling in the range 280 F. to the end boiling point of the blend having an octane rating substantially less than the required octane rating of the blend.

References Cited in the file of this patent UNITED STATES PATENTS 2,249,461 Diwoky July 15, 1941 2,304,187 Marschner Dec. 8, 1942 2,324,165 Layng et al. July 13, 1943 2,434,634 Bates Jan. 20, 1948 2,651,597 Corner et al Sept. 8, 1953 2,891,902 Hess et al. June 23, 1959 2,844,959 Kline et al July 12, 1960 

1. A METHOD OF PRODUCING BLENDED GASOLINE COMPRISING CATALYTIC REFORMATE, STRAIGHT RUN GASOLINE, AND TETRAETHYL LEAD AND HAVING A REQUIRED OCTANE RATING WHICH COMPRISES FRACTIONATING STRAIGHT RUN NAPHTHA TO OBTAIN FRACTION A COMPRISING C5 AND HEAVIER HYDROCARBONS HAVING AN END BOILING POINT OF ABOUT 160*F., FRACTION B COMPRISING HYDROCARBONS BOILING IN THE RANGE OF ABOUT 160* TO ABOUT 320*F., AND FRACTION C COMPRISING HYDROCARBONS BOILING IN THE RANGE OF ABOUT 320* TO ABOUT 380* F., REFORMING ALL FRACTION B AND A PORTION OF FRACTION C, SEPARATING A REFORMATE COMPRISING C5 AND HEAVIER HYDROCARBONS HAVING AN OCTANE RATING HIGHER THAN SAID REQUIRED OCTANE RATING OF THE AFORESAID BLENDED GASOLINE, MIXING SAID REFORMATE, FRACTION A, AND THE UNREFORMED PORTION OF FRACTION C, AND OBTAINING BLENDED GASOLINE HAVING THE AFORESAID REQUIRED OCTANE RATING OF WHICH BLENDED GASOLINE NOT MORE THAN 30 PERCENT BY VOLUME HAS AN OCTANE RATING MORE THAN THREE OCTANE RATING UNITS BELOW THE OCTANE RATING OF THE BLENDED GASOLINE. 